EQ is not the problem. A perfect system will have near 0 levels on all EQ settings. Minute changes on an EQ can have drastic changes for different songs/genres. With a clean amp, power headroom, and amazing components (with matched crossovers) you should have your system tuned with little adjustments from the EQ (focus on the active crossovers). I have tuned my system using an ocilliscope so I have my gains and the EQ near perfect before getting any clipping (and everything is at near zero now - the highest EQ setting is at +2db). However I do believe I need more power in the system to maintain the clean signal.

I have decided to go with the 2nd amp (another Diamond Audio) and I'm scrapping the 8" sub and having a new 10" fiberglass sub enclosure made (with probably a CDT or Eclipse 10" sub). The fronts will run from the 4 channel amp bridged to 200W a channel at 4 ohm. The rear speakers will run from the RAF (rear audio fill) outputs of the component crossovers. The sub will then run from the new 2 channel sub bridged to 600W at 4 ohm. I think this would give me all the headroom I need.

The baffle thing in my current sub helps keep the sub nice and tight and lowers the amount of resanance I get from the plastic rear quarter panel (basically displacing the sound and making a more ambient boom). With the new 10" enclosure I'm going to sound proof the entire rear quarter panel.

I've gone this far with the system so I'm not stopping until I'm REALLY happy.